The science is in: the case for a sugar tax is overwhelming | Robert Lustig

Our new study proves the harm to child health, so cutting public consumption makes political sense

In October 2013, the Mexican Congress did the unthinkable. They passed a peso-per-litre tax on sugared beverages, as well as a similar tax on junk food. This, in a country where some counties still don't have potable water and where the poverty rate is 52%. Last week, the Mexican Congress did something even more unthinkable. They gutted their tax, cutting it by half. This, despite soda tax revenues that topped $19bn a year, and despite a diabetes prevalence rate of 12% compared with the US rate of 9.3%.

The tax caused sugary drink consumption in Mexico to drop 6%. The Instituto Nacional de Salud Publica (the public health officials) called this a success; Hacienda (the treasury department) called it a failure. Why did they gut the tax when it provided revenue to a cash-strapped exchequer?